I am trying to unshelve a shelveset from one Workspace to another.
Both on visual studio online.
Running such a command
tfpt unshelve /migrate /source:"randomname.visualstudio.com\DefaultCollection\Project\Branch1" /target:"randomname.visualstudio.com\DefaultCollection\Project\Branch2" "random_shelveset_name" would result the exception Unable to determin the workspace
The command looks exactly as have been typed in the commandline (the structure of it).
You need to run tf.exe from the command line and run the command:
serverUR being your server information
I had the same issue and had trouble running tf.exe by double-clicking or calling the command without starting tf.exe first